Agricultural sprayers are used by farmers and contractors to apply pesticides and other nutrient-containing solutions to crop fields. Sprayers can be mounted to, or towed by, a tractor or other suitable vehicle or may be self propelled with an integrated means of propulsion and a driver's cab. The sprayer machine typically includes a storage tank for the liquid to be applied, the tank being filled as required by the operator. Alternatively, in systems which offer lower ground pressure, the sprayer machine may be semi-permanently connected by a pipe to a local (field-based) browser wherein the applied liquid is supplied via a pipe from the browser to the sprayer continuously as the latter is repeatedly moved across the crop field.
The liquid is applied to the field by a number of liquid application devises, typically spray nozzles, which are mounted in a spaced relationship along the length of a boom which, itself, is mounted to the sprayer vehicle. The nozzles are each connected to the storage tank by liquid delivery means comprising various pipes, valves, pumps and other plumbing. The liquid is atomized by the nozzles and applied to the crop in a jet of mist for example.
The valves are controlled to switch the flow of pesticide, for example, on and off as required. Due to imperfections in the associated seals, plumbing and the presence of residue fluid on the output side of the valves, dripping of the pesticide from the nozzles and pipework after switching off is often unavoidable. Spillage or unintended application of pesticide is at best undesirable, corrosive and wasteful, and at worst prohibited under local or regional environmental legislation.
Unwanted spillage of pesticide can be reduced by improving or renewing the valves, nozzles and plumbing, but even then prevention of dripping onto the ground below cannot be guaranteed.
Attempts have been made to at least prevent nozzle leakage drips from reaching the ground by providing a drip tray underneath a folded multi-section boom. However, this preventative measure is only effective when the boom is folded for transport.
With respect to the boom itself, the length of the boom determines the operating width of the sprayer. Driven by economies of scale, there is a growing demand for sprayer manufacturers to produce machines with longer spray booms. However, increasing the boom length significantly increases the risk of structural failure due to the increased stress placed upon the hinges and joints caused by natural vibrations and oscillations which pass from the spray vehicle along the boom. Today, boom lengths of conventional truss-style construction are approaching their physical limits with any further increase in length requiring significant strengthening of the joints, mountings and hinges between sections and along the boom.
Therefore, there is a continuing drive to investigate alternative boom constructions which can meet the demands of customers for longer booms.
In addition to seeking improvements in structural integrity of the boom, sprayer manufacturers continuously strive to reduce production costs at the same time as meeting customer demand for a wide range of different sprayer lengths. There is thus a desire to improve modularity in boom construction to reduce inventory on stock without affecting the range of products available.